Trigeminal neuralgia
Exam Tips
- Classic SBA clue: unilateral, electric shock-like facial pain lasting seconds, triggered by light touch, with normal neurological exam between attacks.
- Red flags for secondary causes: onset <40, bilateral symptoms, isolated V1 pain, objective sensory loss, optic neuritis, hearing/ear symptoms, cancer/perineural spread history.
- In UK primary care questions, carbamazepine is first-line and licensed; start low, titrate every 2 weeks, and monitor bloods/adverse effects.
- If carbamazepine fails or is not tolerated, do not keep adding drugs empirically in primary care; refer to neurology/pain specialist.
Definition
Trigeminal neuralgia is a neuropathic facial pain syndrome causing sudden, severe, brief unilateral pain in one or more divisions of the trigeminal (CN V) nerve, most often maxillary (V2) or mandibular (V3). Attacks are typically electric shock-like, last seconds to 2 minutes, recur in paroxysms, and are often triggered by innocuous stimuli such as touching the face, chewing, talking, tooth-brushing, or cold wind.
Pathophysiology
In classical trigeminal neuralgia, the usual mechanism is neurovascular compression of the trigeminal root entry zone (commonly by a looping artery), producing focal demyelination. This causes hyperexcitability of trigeminal afferents and ephaptic cross-talk, so low-threshold tactile input can trigger high-intensity pain discharges. Secondary trigeminal neuralgia occurs when another neurological disorder (for example multiple sclerosis plaques, cerebellopontine angle tumour, cyst, aneurysm, or AVM) damages the nerve pathway; idiopathic cases have no structural cause identified on imaging. Mixed/atypical disease may include persistent background pain between paroxysms, suggesting more sustained nociceptive pathway dysfunction. See Figure: trigeminal divisions (V1/V2/V3) and root entry zone neurovascular conflict.
Risk Factors
- Advancing age (rare under 40; peak around 50-60 years)
- Female sex
- Multiple sclerosis
- Family history of trigeminal neuralgia (uncommon familial clustering)
- Possible association with hypertension and prior stroke
Clinical Features
Symptoms
- Severe unilateral facial pain in trigeminal distribution, usually cheek or lower jaw (V2/V3)
- Pain quality described as electric shock-like, stabbing, sharp, or shooting
- Very brief attacks (seconds to 2 minutes) with abrupt onset and cessation
- Recurrent attacks, potentially many per day, with refractory periods between paroxysms
- Triggerability by light touch, talking, eating, tooth brushing, shaving, washing, or cold air
- Episodic course with remissions lasting weeks to years; some develop persistent interictal aching (mixed/atypical TN)
Signs
- Usually normal cranial nerve examination in classical trigeminal neuralgia
- May have autonomic features during attacks (lacrimation, conjunctival injection, rhinorrhoea/nasal congestion, ptosis, eyelid oedema, facial sweating)
- Red-flag neurological findings suggesting secondary cause: facial sensory loss, hearing symptoms, optic neuritis, bilateral symptoms, isolated ophthalmic (V1) involvement, onset before 40
Investigations
Management
Lifestyle Modifications
- Explain diagnosis and trigger avoidance strategies (e. g, protect face from cold wind, modify chewing/tooth-brushing during flares)
- Use a daily pain diary to track trigger exposure, attack frequency, and response to dose titration
- Screen for depression, social withdrawal, poor oral intake, and weight loss; address psychosocial impact early
- Provide written titration advice and safety-netting, including urgent review for red-flag symptoms
Pharmacological Treatment
First-line anticonvulsant (licensed)
- Carbamazepine immediate-release: start 100 mg once or twice daily; increase by 100-200 mg every 2 weeks; usual maintenance 200 mg three to four times daily; maximum 1600 mg/day
- Carbamazepine modified-release: usual 600-800 mg/day in 2 divided doses; maximum 1600 mg/day
First-line in primary care when no red flags. Titrate gradually; effect may take weeks. Once in remission, taper to lowest effective dose or stop and restart if relapse. Key safety points: check interactions (strong enzyme inducer; reduces efficacy of combined hormonal contraception and interacts with many drugs), monitor FBC/LFT/U&Es, counsel on dizziness/drowsiness, hyponatraemia, and serious rash (SJS/TEN risk; higher in some Asian ancestries with HLA-B*1502). Avoid abrupt withdrawal. Use caution in pregnancy (teratogenic risk) and severe hepatic/cardiac disease.
Specialist-initiated options (often off-label for TN)
- Oxcarbazepine
- Lamotrigine
- Topiramate
- Gabapentin
- Pregabalin
- Baclofen
If carbamazepine is contraindicated, ineffective, or not tolerated, seek neurology/pain specialist input; continue under shared-care where agreed.
Surgical / Interventional
- Microvascular decompression (for neurovascular conflict in medically refractory classical TN)
- Percutaneous ablative procedures (radiofrequency thermocoagulation, balloon compression, or glycerol rhizolysis)
- Stereotactic radiosurgery to trigeminal root entry zone
- Neurosurgical referral is appropriate for severe disabling pain or medication-refractory disease
Complications
- Functional impairment in activities of daily living
- Depression, anxiety, and social isolation
- Weight loss and dehydration from reduced oral intake due to trigger-induced pain
- Medication adverse effects (sedation, hyponatraemia, blood/hepatic toxicity, drug interactions)
- Suicidal ideation risk in severe chronic pain
Prognosis
The condition is typically relapsing-remitting: many patients have clusters of attacks over weeks to months with remission periods that may initially last months to years. Around half experience remissions of at least 6 months, but recurrences are common (about two-thirds within 5 years and over three-quarters within 10 years), and remissions often shorten over time. A minority do not respond to neuropathic pain medication, and mixed/atypical cases with persistent background pain are often more treatment-resistant.
Sources & References
🏥BMJ Best Practice(1)
✅NICE Guidelines(1)
- Trigeminal neuralgia[overview]